1. Field of the Invention
The present invention relates generally to the construction of chairs suitable for use in an office environment and more particularly to a chair which offers improved comfort due to its particular control of back tilt and seat tilt functions.
2. Description of the Prior Art
Many attempts have been made to improve the comfort of chairs used in the vagaries of office environments. Chairs are well-known, for example, which have a tiltback feature wherein the back of the chair tilts rearwardly as the forward edge of the chair tilts up. In a simple form, such a chair may have its back and seat immovably connected relative to one another and supported by a control assembly which is pivotable with respect to the chair base and which includes one or more springs for biasing the seat and back to a normally neutral position. However, in such chairs, as the user leans back, the forward portion of the seat exerts upward pressure on the upper legs of the user and can impair blood circulation in the user's legs. Such a result can be uncomfortable to the user. Also, excessive seat tilt can tend to raise the user's feet from the floor thereby causing the user to lose stability while leaning back in the chair.
In order to alleviate the problems associated with excessive seat tilt, chair controls have been developed, known as synchronous controls, which provide for different rates of tilt of the back and seat. With such a control, there is typically a greater degree of back tilt to seat tilt. The user can thereby lean well back in the chair without experiencing excessive pressure on his or her legs and without raising the feet from a firm position on the floor. An example of such a control is disclosed in U.S. Pat. No. 5,318,345 issued to Olson and assigned to the common assignee herein.
While synchronous controls of the foregoing type improve over the prior art in terms of chair comfort, they are typically complex in construction and represent a substantial cost in the manufacture of a chair. Another characteristic of these chairs is that in order to effect synchronous movement of the seat and back, the back typically has its pivot axis located beneath the seat. This arrangement causes the back of the chair to have an excessive downward component of movement as the user leans back in the chair. Thus, the chair back does not pivot in a manner which corresponds to the normal movement of the user's body. Moreover, a common disadvantage of such chairs is that the differential pivotal movement of the back relative to the seat creates an undesirable frictional effect on the user. Such an effect can manifest itself as an annoying phenomenon known as "shirt pull" wherein the shirt of the user becomes dislodged from the skirt or trousers. A further disadvantage of prior art chairs is that they lack a comfortable forward tilt feature which is often desirable for task intensive office environments.
Accordingly, it is desirable to provide a chair construction which is economical to manufacture and which also offers improved comfort over prior art constructions. It is further desirable to provide such a chair having a seat and back which are not restricted to a predetermined conjoint movement whereby the seat and back can adjust to a variety of user body positions. Still further, it is desirable to provide such a chair wherein the back pivots about an axis which more normally corresponds to the movement of the user's body. It is further desirable to provide such a chair with a comfortable forward tilt feature such that the chair is readily adaptable to being used in task intensive environments.